Method for driving piles and similar objects



Dec. 24, 1968 DUYSTER ETALY 3,417,828

METHOD FOR DRIVING FILES AND SIMILAR OBJECTS Filed Feb. 5, 1966 2Sheets-Sheet 1 FIG. 3 FIG. 4

9 ll L0 2 6 FIG. 2 FIG. 5 3 j ll-llll g 1 7 /6 4 l K? i 5 243E111 9 mFIG. 6

Dec. 24, 1968 c, DUYSTER ETAL 3,417,828

METHOD FOR DRIVING FILES AND SIMILAR OBJECTS Filed Feb. 3, 1966 2Sheets-Sheet 2 FIG.

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\ ///Y /1//////// ll/l/ I /6 Fl 6; 9 I I United States Patent 3,417,828METHOD FOR DRIVING PILES AND SIMILAR OBJECTS Hoite C. Duyster, TheHague, Sybrand Noyon, Bennekom, and Joost W. Jansz, The Hague,Netherlands, as-

signors to Hollandse Beton Maatschappij N.V., The

Hague, Netherlands Filed Feb. 3, 1966, Ser. No. 524,773 Claims priority,application Netherlands, Feb. 3, 1965, 6501373; Jan. 24, 1966, 660086320 Claims. (Cl. 175-19) ABSTRACT OF THE DISCLOSURE A pile drivingapparatus having a resilient cap or shoe between the pile head and thehammer, said cap or shoe being precompre-ssible and maintainable in aparticular state of precompression such that when the hammer strikes thecap, substantially no energy is lost by dissipation and the maximumimpact force which is transmitted through the cap to the pile is lessthan the critical force at which the pile is damaged.

This invention relates to a method of driving piles and the like, inwhich use is made of a hammer, which is dropped from some height andtrasmits its kinetic energy to the pile when the blow strikes the pilehead.

The impact force created during the energy transmission from the hammerto the pile may in practice not exceed such a value that the pile headis shattered. In order that the pile may penetrate into the ground, theimpact force should however at least reach a minimum value, whichdepends upon the nature of the ground. If the pile may not be subjectedto tensile stresses, or may only be subjected to low tensile stresses,the energy transmission must occur within a minimum time period, whichamong other factors depends upon the pile length and the impact diagram.

T o satisfy the above conditions, a so-called cap is often used, aresilient, but if exceeding a certain compressive force, permanentlydeformable means, which is placed between the pile head and the hammer.In its usual form the cap comprises a steel jacket, retaining elasticmaterial with stiff resilience, usually composed of hard wood, that mustbe loaded parallel to the fiber, in the form of a plug, with under it asoft wood filling, which should be loaded perpendicular to the fiber.This cap is considered on the one hand to render a reasonable forcedistribution on the pile head by elastic deformation, and on the otherhand to prevent the impact force, exerted on the pile, from exceeding avalue, which is dangerous for the pile, by dissipating a portion of theenergy by permanent deformation-scatter-of the wooden filling. The softwood filling soon loses its deformability so that it is necessary toperiodically replace said filling. By using such a cap a time-impactforce diagram is obtained, wherein a rather considerable portion of theimpact force is usually below the aforesaid required minimum. For thatreason also the energy is imperfectly transmitted. Finally, when usingsuch a cap, both the resulting impact diagram and the duration of theimpact among others depend upon the deformability of the filling, whichdecreases as a result of the hammering action, and are both by no meansoptimally favorable for reducing the aforesaid tensile stresses in thepile. Instead of soft wood other materials, such as rubber and plastics,are used for the filling of the cap, but these also cannot eliminate thedisadvantages of the known method. These disadvantages moreover requirethat for driving longer and heavier piles heavy hammers must be used.

According to one aspect of the present invention an improved method ofdriving piles and the like is provided, and an apparatus which may beused for the purpose, in which the kinetic energy of the hammer is morecompletely utilized, because the useless consumption of energy in theinitial and final periods of the impact is avoided and the necessity ofdissipating energy by permanent deformation is eliminated by providing aresilient means between the hammer and the pile head, characterized bycreating and maintaining a precompression in said resilient means, sothat immediately from the beginning under each hammer blow the minimumrequired force, sufficient to overcome the ground resistance, will beavailable, while under the impact said resilient means is deformed to arelatively great extent, with a corresponding relatively small increaseof the force.

It is a further object of the invention to provide a timeimpact forcediagram of such favorable form and duration in which even in relativelylong piles the creation of tensile stresses with certainty can beavoided. This object is achieved by eliminating the permanentdeformation and by proper selection of the resilient means.

In order that the invention and its advantages may be more clearlyunderstood, reference will now be made to the accompanying drawings, inwhich:

FIGURE 1 schematically shows the graph of the force exerted on the pileduring each striking action, plotted in a time-impact force diagram,when using the known cap.

FIGURES 2-5 show the principle of the device according to the presentinvention.

FIGURE 6 shows a time-impact force diagram obtained by using the deviceaccording to the invention, and also the theoretically optimum diagram.

FIGURES 7-9 are sections of various embodiments.

FIGURE 10 is a section of a complete hammer, with a built-inprecompressed resilient means in accordance with the invention, in whichthe value of the precompres sion is automatically maintained.

FIGURE 11 is a partial view of the top of FIGURE 10 showing the controlvalve in a different position.

FIGURE 1 schematically represents a stroke diagram, in which the level Pindicates the minimum force required to overcome the ground resistance,opposing the penetration of the pile, and P represents the maximum forcethat is, the force which should not be exceeded in order to preventdamage to the pile. Such a diagram as the following disadvantages:

(1) The energy transmitted from the hammer over the time 0-11 and t t isuseless because the impact is then smaller than the force P which isnecessary to overcome the ground resistance.

(2) Because of its more or less triangular shape the diagram has arelatively high apex, so that the critical force P can be reached quitetoo easy.

(3) The maximum impact force is achieved in a very short time t already,so that when driving relatively short piles, relatively high tensilestresses may occur.

Since by increasing the drop height the time length of the diagram ishardly increased but the maximum impact force does increase, andconsequently both the danger of shattering the head of the pile iscreated and in case of longer piles the creation of non-allowabletensile stresses, in practice the required energy for the driving actioncannotbe obtained by dropping a hammer of relatively light weight over agreat height,but a relatively heavy hammer must be used which requires aheavier installation and is accomplished at the cost of mobility.

In the embodiments according to the invention for the compressiblefilling of the resilient means, which is mounted between the pile headand the hammer, a material or combination of materials is selected,which is capable of resiliently receiving the entire fall energy of thehammer, thus enabled by the said precompression principle, whereby themaximum force created thereby, can be previously determined at a valuewhich prevents damage to the pile.

The thereby obtained time-impact diagram is shown in FIGURE 6, whereinthe theoretically optimum diagram is shown in the shaded portion. Thediagram clearly shows the following favorable characteristics:

(1) The minimum required force P is very rapidly reached and untilpractically the last instant of the impact at least maintained, so thatno useless energy is transferred to the pile.

(2) The maximum value P of the diagram can previously and exactly bedetermined and with certainty be fixed below the critical value P (3)The maximum impact force is not reached until after a relatively longtime i so that only in relatively long piles do tensile stresses occur,which moreover in that case are not proportional to P but to the so muchsmaller value P P As a result of the relatively long impact duration ithe invariable minimum value of which may previously be determined, onlyin very long piles can tensile stresses of any significance exist, whichin such case are proportional to P The improved apparatus according tothe invention is substantially based on the following principles:

(1) The construction 1, positioned between the pile head 2 and thehammer 3, which will be elastically deformed by the dropping hammer 3during the impact, is already precompressed to a certain extent by aforce, operating in the same direction as the impact force of the hammer3.

Compression of the construction 1 by the falling hammer 3 will not bepossible until the impact force has reached the Value used for theprecompression. FIGURE 2 shows an example hereof, in which the helicalspring 4 is precompressed by tightening the bolts 5.

(2) The elastic material 6, which will be compressed by the hammer 3 isprecompressed under uniform pressure, so that compression is notpossible until the impact force of the hammer 3 has created the samepressure in the elastic material 6. FIGURE 3 shows an example hereof, inwhich in a cylinder 7 under a piston 8 a gas 6 is precompressed, with acollar 9 of the cylinder 7 limiting the stroke length of the piston 8.

(3) The medium 10, which must be deformed by the hammer 3, issubstantially incompressible, but readily deformable. This deformationis opposed by an elastic construction 11, which is precompressed, sothat deformation by hammer 3 is not possible until the impact force hascreated a pressure in the medium 10, which is equal to theprecompressed. FIGURE 4 shows an example hereof, within a cylinder 7under a piston 8 a liquid 10 being present, which is precompressed by apiston 12, on which in the housing 13 the spring 14 operates. Thecollars 9 and 15 limit the stroke lengths of the respective pistons 8and 12.

(4) In the housing 7 is a flying piston 16 having on one side theincompressible, but readily deformable medium 10 and on the other sidethe gaseous medium 6. At one end of the housing 7 is closed by thepiston 8, with the stroke length thereof being limited by the collar 9,as is indicated in FIGURE 5. The medium 10 is precompressed by means ofthe gas 6.

The stroke diagram of all the basic embodiments may be representedschematically as shown in FIGURE 6. The buckling point A in the diagramwill be at a pressure level P determined by the precompression. Thedisplacement to reach A is determined by the deformation of thestiff-elastic construction 1 as a result of the precompression, that isthe elongation of the bolt in FIGURE 2, the deformation of the cylinder7 and the collar 9 in FIGURES 3, 4 and 5. Since said censt uc i t 1, inview of the great forces, will be very stiff, the displacement to reachpoint A will be small, so that the graph 0A in the diagram will be verysteep.

The following part AB of the graph is determined by the force requiredto deform the resilient construction, that is the spring 4 and 14respectively in FIGURES 2 and 4 and the gas column 6 in FIGURES 3 and 5,so that the slope of AB can be adjusted within wide limits by theselection of materials and volumes.

According to the invention there are selected, firstly, such aprecompressed in the resilient means that the buckling point A will beabove or at least close to the level P (FIGS. 1 and 6) which indicatesthe minimum force required to overcome the ground resistance opposingthe penetration of the pile, and secondly, such a low modulus ofelasticity of the resilient means that the point B will remain below thelevel P which represents the force which should not be exceeded in orderto prevent damage to the piles. Accordingly the pile cannot be damaged,even if the pile does not penetrate at all. The deformation in theresilient means will proceed entirely elastic, so that in said meanslittle or no energy is lost.

According to the invention the steep onset of the graph 0A in thediagram according to FIGURE 6 has moreover the great advantage, that theextent of the deformation of the elastic means under the influence ofthe blow is limited in proportion to the energy transmission, so thatthe development of heat in the elastic means remains low, which isaffirmed by experiments. Thus, materials may be used, which withoutprecompression would soon be unusable because of heating.

FIGURE 7 shows a basic drawing according to the invention, in which thegas of FIGURE 3 is replaced by a cylindrical element 17 of soft rubberor similar material, which is retained between steel plates 18, linkedby one or more bolts 5, and in which a uniform precompression is createdwithout deformation by a binding 19 with a string which is wound understress, or a strip of an elastic material such as rubber.

FIGURE 8 shows a suitable further development of the principle of FIGURE4, in which the core 20 of rubber or similar material is enclosed by ahollow metal cylinder 21, composed of adjacent thin radial lamellas,bearing upon the metal edges 22. The hollow cylinder 21 is wrapped witha string or similar strip of elastic material 19 under stress. Withsufficient load the core 20 can push the lamellas 21 of the cylinderapart against the force exerted by the material 19.

FIGURE 9 shows a suitable further development according to the principleof FIGURE 3, in which, however, the gaseous medium 6 is precompressed ina deformable envelopment 23 of rubber or similar material, which issupported on all sides by the housing 7 and the therein located piston8, with the displacement of which is limited by the collar 9.

FIGURES 10 and 11 show a complete pile driving apparatus according tothe invention, of which the hammer incorporates the precompressedresilient means, with means whereby the value of said precompression isautomatically maintained. The hammer is provided at its lower end withthe resilient means according to the principle of FIGURE 5, in which thespace with the liquid medium 10 being connected thru a conduit 24,incorporating a non return valve 25, scaling in both directions, withthe space 26 above the piston 27 in a vertical bore in the hammer 3. Thepiston 27 is carried by a hollow piston rod 28 which is integral with orfixed to the end wall 29 of a housing 30 in which the hammer 3 moves,the bot tom of the housing 30 being provided with an anvil plate 31, andguiding means 32 for the pile 2. The hollow piston rod 28 is provided atthe lower end with openings 33 communicating with the space 26 above thepiston 27, and is connected at its upper end to a three-way controlvalve 34 carried by the end wall 29. The three-way control valve can beoperated to connect the hollow piston rod through a conduit 35 with apump for pumping and compressing the liquid medium (FIGURE or to aconduit 36 (FIGURE 11) discharging into the liquid supply tank. Thespaces or conduits 10, 24, 26, 28, 35 and 36 are continuously filledwith the liquid medium. The liquid in the space 10 also serves as a sealto prevent leakage of the compressed gas 6.

The operation of the apparatus is as follows:

With the three way valve 34 in the position of FIGURE 10 liquid isintroduced under pressure through conduit 35 and the hollow piston rod28 and openings 33 into the space 26. This hydraulic pressure on theeffected piston area of the piston 27 causes an upward force on thehammer 3, which moves upward in the housing 30 with a velocity, which isdependent upon the pump capacity. When it reaches its uppermostposition, the hammer 3 produces an impulse which causes the three waycontrol valve 34 to change from the position shown in FIGURE 10 to theposition shown in FIGURE 11, so that the space 26 above the piston 27,which is filled with the liquid medium, is now in open communicationthrough the openings 33, and the hollow piston rod 28 with the dischargeconduit 36. The hammer 3 can fall freely in the housing 30 under theforce of gravity, the liquid medium being expelled from the space 26without causing resistance, since the channels and conduits are ofsufficiently -large dimensions. In its lowermost position, the hammer 3,through its ram 8 which projects below the bottom of the hammer, hitsthe anvil plate 31 and transmits its kinetic energy to the pile 2. Arelatively thin plate of a suitable material (not shown) may be locatedbetween the anvil plate 31 and the pile 2 to ensure a uniform forcedistribution on the pile head. During this impact the precompressedresilient means situated at the bottom of the hammer 3, will functionaccording to the diagram of FIG- URE 6. Depending upon the energyabsorption by the pile 2, which is again dependent upon the resistanceof the ground, the hammer 3 will more or less bounce up in its housing30, at the time of impact an impulse is produced to operate thethree-way control valve 34 to change its position back to that shown inFIGURE 10, whereby the space 26 above the piston 27 is again pressurizedby the pump and the hammer 3 is moved. To maintain constant thecompression of the gas 6 in the cylinder chamber above the free piston16, during each upward movement of the hammer 3, a communication isestablished via the non return valve 25 and the conduit 24 with theliquid filled space 10 below the piston 16. By employing a return valve25 of such construction that it will only open until a preliminarydetermined and adjustable pressure valve, and provided that this valueis below the pressure which must be created in space 26 in order to movethe hammer 3 upwards, it is possible to ensure that, during each upwardmovement of the hammer 3, the desired pressure of the liquid medium inthe space 10 will be automatically maintained or restored .prior to thenext impact. The herein described method is adaptable to a fullyautomatically operating hammer. The transferred energy can be regulatedduring the operation by modifying the drop height, which could, forexample, be accomplished by producing the impulse for changing the threeway control valve 34 from the position shown in FIGURE 10 to theposition shown in FIGURE 11, before the end of the upward movement ofthe hammer 3. Externally operated means may be provided for adjustingwhen said impulse is automatically created. A further refining forincreasing the efficiency of the apparatus consists in providing anaccumulator in the supply conduit 35, so that the intermittentlyrequired maximum output from the pump can be obtained by a continuousoutput, from a smaller pump.

It should be understood that the present disclosure is for the purposeof illustration only, and that this invention includes all modificationsand equivalents which fall within the scope of the appended claims.Accordingly the invention may, for example, be applied to driving intothe ground of embankment constructions and other similar objects, and,in fact to any application where the characteristic of the precompressedresilient means is utilized, irrespective of the ultimate purpose of itsuse.

We claim:

1. A method for driving a pile comprising applying an impact force to aregulable resistancedevice interposed between theforce and a pile to bedriven, adjusting the resistance in said device such that upon initialapplication of the force to the device, the force is unyieldinglyresised such that the force builds up to a predetermined intensity abovea particular minimum value, after which the force is transmitted to thepile by said device at an intensity level below a predetermined maximumvalue as established by the magnitude of resistance adjustment.

2. A method as claimed in claim 1 wherein said resistance in said deviceis adjusted to a particular value such that when the applied forceexceeds a preestablished maximum intensity, the resistance yields andtransmits to the pile a force which is lower than a preestablishedmaximum value which is to be applied to the pile.

3. Apparatus for the driving of a pile by the blows of a hammer, saidapparatus comprising means in the path of the hammer for receiving theblows therefrom and for transmitting, to the pile to be driven, a forcewhich has a value between a predetermined minimum and a predeterminedmaximum, said means comprising a regulable and precompressible deviceadjusted to a predetermined elas tic resistance for receiving the energyof the blows and for transmitting said energy to the pile as a forcewhich has a value between said minimum and maximum.

4. Apparatus according to claim 3 wherein said regulable andprecompressible device includes a compressible substance and means forprecompressing the substance to a preestablished degree whereby thelatter has a predetermined elastic resistance for transmitting theenergy of the blows to the pile.

5. Apparatus according to claim 3 wherein said precompressible deviceincludes a cap containing a compressible substance.

6. Apparatus according to claim 5 wherein the means for precompressingthe substance comprises at least one elastic tie connection.

7. Apparatus according to claim 4 wherein said substance is a gaseousmedium and said means for precompressing the substance includes a devicefor directly compressing the gaseous medium.

8. Apparatus according to claim 3 'wherein said substance is a liquidmedium.

9. Apparatus according to claim 5 wherein said cap comprises a solidmaterial of elastic composition.

10. Apparatus according to claim 9 wherein said cap comprises an upperand a lower plate, said elastic material being retained between saidplates, at least one tie bolt connecting said plates so that aprecompression of the elastic material may be effected.

11. Apparatus according to claim 4 wherein said compressible substanceis a rubber core and said precompressing means comprises elasticmaterial wound on said core with prestress.

12. Apparatus according to claim 11 wherein said precompression deviceincludes a hollow metal cylinder comprising adjacent thin radiallamellas, which are centered by edges, said rubber core being disposedin the cylinder, said prestressed elastic material encircling saidcylinder.

13. Apparatus according to claim 4 wherein said precompressible deviceincludes a cap, said substance being a gaseous substance, and a rubbercontainer in said cap for containing the gaseous substance.

14. Apparatus according to claim 4 wherein said precompressible deviceincludes a'cap, said substance being a gaseous substance, said capdefining a space for said gaseous substance, said means forprecompressing the substance including a piston closing said space inpart and in contact with the gaseous substance, and means for displacingthe piston to regulate the pressure of the gaseous substance in saidspace.

15. Apparatus according to claim 3 wherein said hammer and saidprecompressible device are constituted as a unitary assembly whichincludes a housing containing said hammer and said precompressibledevice.

16. Apparatus according to claim 15 wherein said precompressible devicedefines a space containing said compressible substance which is agaseous medium, said precompressing means comprising a piston boundingsaid space in part and in contact with the gaseous medium therein, andmeans for displacing the piston under the pressure of a liquid medium toregulate the pressure of the gaseous medium in said space.

17. Apparatus according to claim 16 wherein said space and piston arecontained in the hammer which moves up and down, and said precompressingmeans includes means for regulating the pressure of said liquid medium,which acts on the piston, during each upward movement of the hammer.

18. Apparatus according to claim 17 wherein said precompressing meanscomprises a valve means for controlling the supply of the liquid mediumto the piston and the means for regulating the pressure of the liquidmedium includes a non-return valve between said piston and the valvemeans for maintaining the pressure of the liquid acting on the piston ata constant value during upward movement of the hammer.

19. Apparatus according to claim 18 wherein said assembly comprises ahollow piston fixed in said housing, said valve means being a three-wayvalve coupled to the hollow piston for selectively supplying the samewith pressurized liquid medium or withdrawing the pressurized liquidmedium, said hammer being slidably mounted on said hollow piston, saidhammer having a passageway connecting the hollow piston with the movablepiston via said non-return valve, said hammer having a chambersurrounding the hollow piston which is adapted for receiving thepressurized liquid medium to raise the hammer.

20. Apparatus according to claim 19 wherein said three-way valve isoperated in synchronization with the piston to connect the three-wayvalve in alternation with the supply of pressurized liquid medium andexhaust.

UNITED STATES PATENTS References Cited 2,660,403 11/1953 Roland 192,972,871 2/1961 Foley 17519 X 3,001,515 9/1961 Haage 61-53.5 X3,100,382 8/1963 Muller 17519 X 3,106,258 10/1963 Muller 175-19 X3,312,295 4/1967 Bodine 17519 3,316,722 5/1967 Gibbons 6153.5 X

NILE C. BYERS, JR., Primary Examiner.

US. Cl. X.R.

